1. Field of the Invention
This invention relates to a method of synthesizing certain bis-sulfones and to intermediates useful in the preparation thereof.
2. Description of the Prior Art
The synthesis of 2-lithio-1,3-dithianes by reacting a dithiane with n-butyllithium in tetrahydrofuran (THF) at -20.degree. C. is described by D. Seebach and E. J. Corey, J. Org. Chem., 1975, 40, p. 231. These authors also report the reaction of 2-lithio-1,3-dithianes with aldehydes, ketones, carboxylic acid derivatives and various other common electrophiles in THF at -20.degree. to -70.degree. C. The dehydration of certain of the resulting ketone and aldehyde adducts with, for example, p-toluenesulfonic acid to give the ketene thioacetals, i.e., the alkylidenedithianes also is described. The oxidation of alkylidenedithianes with m-chloroperbenzoic acid to give the corresponding bis-sulfones is reported by E. J. Corey and G. Markl, Tetrahedron Letters, 1967, p. 3201.
The present invention is concerned with a method of synthesizing these bis-sulfones which employs a blocked intermediate.